This invention relates to an adjustable steering device for motor vehicles comprising a steering spindle which is axially adjustably displaceably mounted in a jacket tube.
An axially adjustable steering device for motor vehicles is known from German Patent Document DE-33 18 935 C1. In the case of this device, a motor-driven pinion is constantly engaged with a protecting steering tube by way of a toothing. This protective steering tube is fixedly connected with the steering spindle and can be displaced by way of the pinion.
Furthermore, from U.S. Pat. No. 2,836,988, an axially adjustable steering column is known in the case of which a spindle nut is caused to rotate by way of a motor-driven pinion. This spindle nut acts upon a protective steering tube which is connected with the steering spindle and is therefore axially displaced.
It is an object of the invention to provide an improved adjustable steering device which ensures a simple and secure axial adjustment and fixing while exhibiting good crash accommodating characteristics.
According to the invention, this object is achieved by providing an arrangement wherein the adjusting element includes at least one pressure segment which is held by means of an elastic tensioning element on a protecting steering tube which has a toothing, said pressure element having a toothing which is movable between a fixing and a displacement accommodating position by means of a tensioning device which controls the interengagement of the toothing on the protective steering tube and on the pressure element.
By means of the invention, it is mainly achieved that, in addition to an axial adjustment of the steering wheel carried by a steering spindle, an optimal energy absorption is achieved also in the case of a crash by way of an integrated deformation element.
The axial adjustment takes place essentially by way of a pressure segment of an adjusting element which, by means of a toothing, is engaged with a protective steering tube for fixing purposes and can be disengaged for the axial displacement.
In an advantageous further development of the invention, an energy absorption in the case of a crash is achieved by means of a deformation element in the form of a corrugated tube or of a reversed tube which is arranged between the pressure piece and a lower end of a jacket tube surrounding the protective steering tube.
In an advantageous further development, the pressure segment is held in a receiving ring and has a toothing which is correspondingly opposite a toothing of the protective steering tube. The operating of the adjusting element or of the pressure piece for taking up a fixed position and a displaced position takes place by way of a tensioning device consisting of a tensioning element. This is connected with an adjusting rod of a handle and can be adjusted by a rotating or a displacing so that the steering spindle can be brought into the displacement position or into the fixing position.
In certain preferred embodiments, tensioning element of the device acts directly in a flat manner on the pressure segment which can be rotated and/or displaced by way of the adjusting rod of the handle, and an adjustment or a fixing of the steering spindle can therefore be carried out in a simple manner. An axial displacement of the steering spindle and thus an adjustment of the steering wheel into different positions with respect to the driver takes place in the loose position in which the toothings slide on one another corresponding to a ratchet effect. The pressure segment is held by way of the elastic tensioning element in the receiving ring in such a manner that, when the steering spindle or the protective steering tube is axially displaced, the pressure segment is pressed out of the toothing of the protective steering tube. The tooth-on-tooth position is avoided as a result of the elastic tensioning element.
In various further developments, the tensioning element may consist of an eccentric, a curved piece or a conical part. For connecting the adjusting rod with the handle, a hexagon fitting or the like is provided on the tensioning element.
The adjustment of the tensioning element may take place manually or by means of a motor, a corresponding switch being provided on the dashboard for the adjustment by means of a motor, by means of which switch the axial adjustment may be switched on and off.
For limiting the axial displacement, a longitudinal slot is provided in the protective steering tube into which a stop sleeve projects, and a starting position and end position can therefore be fixed. The jacket tube may have an impression whose shoulder strikes against the bearing of the pressure piece during the adjustment.
For absorbing energy in the case of a crash, a deformation element is connected with the adjustment element, which deformation element is supported on the receiving ring for the pressure segment. The opposite, facing-away end of the deformation element is held on a bearing ring which is fixed to the jacket tube by way of a snap ring. The deformation element can therefore be mounted in a simple manner in that the bearing ring is removed. During the mounting, the prestressed crash element is used as a spring element--tolerance compensation--and holds the mounted parts under prestress (noiselessness).
The actual receiving space for the adjusting device in the jacket tube in certain preferred embodiments has a larger diameter than the adjoining jacket tube, whereby advantageously a supporting wall is created for the receiving ring and therefore also for the deformation element. Furthermore, this receiving space is dimensioned such that optionally an adjusting device, which has a receiving ring and a pressure segment, may be accommodated as well. This adjusting device comprises a spindle nut which can be driven by a pinion and which moves by way of a toothing on the jacket tube, in which case the pinion can be driven by a motor or manually.
In certain preferred embodiments, bearings of the jacket tube on the vehicle body are selected such that the lower bearing is provided approximately in the center of the deformation element and between two bearings adjacent to the lower bearing of the adjusting element.
According to certain preferred embodiments with a simplified and lower-cost device, the outer jacket tube surrounding the protective steering tube is provided with a recess in which the pressure piece is held in a radially displaceable manner between outwardly projecting walls. The tensioning device is also disposed in these walls so that a constructionally simple solution is obtained for the axial adjustment of the steering column. A deformation element is not provided in the case of this device.